Metacrangon proxima Kim, 2005

Komai, Tomoyuki, 2012, 3468, Zootaxa 3468, pp. 1-77 : 68-71

Metacrangon proxima Kim, 2005

( Figs 37, 38, 42)

Metacrangon proxima Kim, 2005: 242 , figs 1–3; Komai 2011: 286; De Grave & Fransen 2011: 458 (list).

Material examined. Non-type. Japan. RV Seiyo-maru , 1994 cruise, stn S9, Sagami Bay , 35°05.9’N, 132°32.0’E, 742–748 m, 14 May 1994, 14 males (cl 4.0– 5.2 mm), 17 females (cl 3.8–8.2 mm), 2 ovigerous females (cl 6.6, 8.3 mm), 3 juveniles (cl 3.1–3.8 mm), CBM-ZC 9537; stn S12, Tateyama Bay , Sagami Sea, 35°00.4’N, 139°48.0’E, 411 m, 14 September 1994, sledge, 2 males (cl 4.2, 4.4 mm), 1 juvenile (cl 3.0 mm), CBM-ZC 9538. RV Tanseimaru, KT 95-5 cruise, stn TB-14, SE of Cape Taito , Boso Peninsula , 35°09.1’N, 140°48.2’E, 311–325 m, 26 April 1995, beam trawl, coll. T. Komai, 2 males (cl 4.6, 5.0 mm), CBM-ZC 9539; KT98-14 cruise, stn 17-1, off Katsuyama Ukishima Islet, Uraga Strait, 35°07.177’N, 139°49.114’E, 281–298 m, 30 August 1998, dredge, coll. T. Komai, 1 ovigerous female (cl 8.4 mm), CBM-ZC 9540; KT04-6 cruise, stn KN-1(2), Shima Spur, Kumano Sea, 34°00.86’N, 136°54.32’E to 34°00.20’N, 136°55.50’E, 767–771 m, 1 May 2004, beam trawl, coll. H. Kohtsuka, 1 male (cl 5.2 mm), 1 ovigerous female (cl 7.0 mm), CBM-ZC 10674; stn KN-1(3), similar locality, 33°59.56’N, 136°55.12’E to 33°58.95’N, 136°55.86’E, 763–796 m, 1 May 2004, beam trawl, coll. H. Kohtsuka, 2 males (cl 4.7, 5.0 mm), 1 female (cl 6.7 mm), CBM-ZC 10675; stn KS-2(2), Kinsuno-se Bank, 34°18.05’N, 138°14.75’E, 344– 393 m, dredge, 30 April 2004, 1 female (cl 5.6 mm), CBM-ZC 10676. SE of Katsuyama Ukishima Islet, Uraga Strait, 200–250 m, 19 March 2007, gill net for scampi, coll. S. Tsuzuki, 1 female (cl 6.9 mm), CBM-ZC 9212 .

Type material. Holotype: Amadaiba , Sagami Bay, 280 m, 25 July 1953, female (cl 8.2 mm), NSMT-Cr R751 . Not examined.

Diagnosis. Rostrum ( Figs 37A, B, F, 38D) triangular with blunt to acute tip in dorsal view, directed forward to somewhat ascending (angle about 30° against horizontal plane of carapace at most), extending as far as or slightly overreaching antennal teeth (less than 0.2 times as long as carapace); ventral carina row. Carapace ( Fig. 37A, B) with anterior middorsal tooth slightly larger or subequal to posterior tooth, arising at 0.2 of carapace length (female) or 0.3 (male); posterior tooth arising at about 0.6 of carapace length; submedian teeth present; antennal tooth directed forward in dorsal view, ascending in similar degree to rostrum in lateral view, acute or subacute; branchiostegal tooth moderately strong, directed forward in dorsal view, ascending in similar degree to rostrum in lateral view; postorbital angle slightly produced; orbital cleft present. First abdominal somite rounded dorsally, second somite rounded or with trace of middorsal carina, third and fourth somites each with broad, less clearly delimited middorsal carina, fifth somites with broad, distinct middorsal carina ( Fig. 37C, D). Sixth abdominal somite ( Fig. 37D) with distinct submedian carinae. Telson ( Fig. 37D) with anterior pair of dorsolateral spines located slightly posterior to midlength. Eye ( Fig. 37F) 1.1–1.2 times longer than wide. Antennular peduncle slightly overreaching midlength of antennal scale; first segment with short blunt distolateral process; stylocerite terminating in acute or subacute tooth, not reaching distolateral process of first segment; second segment with short, blunt distolateral process. Antennal scale ( Fig. 37F) about 0.5 times as long as carapace and 2.6–3.2 times longer than wide; lateral margin concave or sinuous; distolateral tooth reaching distal margin of roundly triangular lamella. Third maxilliped with ultimate segment 6.5–7.0 times longer than wide ( Fig. 38A). First pereopod with palm 2.9–3.4 times longer than wide (female) ( Fig. 38B) or 3.5 times (male).

Description. See Kim (2005).

Coloration. Not known.

Size. Largest male cl 5.2 mm; largest female cl 8.3 mm, ovigerous females cl 6.6–8.3 mm.

Distribution. Restricted to the Pacific coast of central Japan from off Cape Taito, Boso Peninsula to Kumano Sea ( Fig. 42); at depths of 200– 771 m.

Remarks. This species was originally described on the basis of three females and one male from the Sagami Bay, central Japan ( Kim 2005). Kim (2005) stated that Metacrangon proxima was very similar to M. variabilis . He cited 12 characters of possible significance in differentiating M. proxima from M. variablis . The present material enables an assessment of the morphological variation in M. proxima , and it is clarified that the following characters are most significant to distinguish the two species: the middorsal and submedian teeth on the carapace are distinctly stronger in M. proxima than in M. variablis ; the antennal scale is relatively narrower in M. proxima than in M. variablis (2.6–3.2 times as long as wide versus 2.2–2.4 times as long); and the palm of the first pereopod is relatively slender in M. proxima than in M. variablis (in females, 2.9–3.4 times as long as wide versus 2.6–2.9 times as long).

Metacrangon asiaticus is also very similar to M. proxima . Nevertheless, M. proxima differs from M. asiaticus in having stronger middorsal and submedian teeth on the carapace (cf. Fig. 33B and Fig. 37B for females, Fig. 36A and Fig. 38A for males), the proportionally longer antennal scale (about 0.5 times as long as the carapace versus 0.4 times as long), the more slender ultimate segment of the third maxilliped (6.5–7.0 times longer than wide versus 4.0–4.5 times) and the more slender palm of the first pereopod (2.9–3.4 times as long as wide versus about 2.4 times as long).